The present invention relates to an eyeglass lens processing apparatus for processing a periphery of an eyeglass lens and an eyeglass lens processing method.
In an eyeglass lens processing apparatus, a periphery of a lens is processed on the basis of target lens shape data which is obtained from a rim (lens frame) of an eyeglass frame or a dummy lens. As for eyeglass frames, there are a rim type, a Naylor type (half rimless type), and a rimless type. In the case of the rim type, a bevel is formed on a periphery of the lens by a bevel processing tool to hold the lens in a groove of the rim. In the case of the Naylor type, a groove is formed in a periphery of the lens by a groove cutting tool. In the case of the rimless type, a hole is formed in a refractive surface of the lens by an endmill or the like. In recent years, an apparatus which permits bevel processing, groove processing, and drilling by one processing apparatus has been put to practical use (JP-A-2003-145328).
Incidentally, a metal frame is provided with a pair of nose pad arms, each having a curved shape for supporting a nose pad. For example, FIG. 7 shows an example of a rim type frame. A nose pad arm KA for supporting a nose pad NP is attached to a rim RM. The nose pad arm KA has a complexly curved shape in order to appropriately adjust the distance between the lens and an apex of the cornea of the eye or to allow the nose pad NP to be snugly brought into contact with the wearer's nose.
In general, a bevel is often formed at a periphery of the lens, which is fitted to the rim RM, such that the amount of projection of the lens toward the front side of the rim RM does not become excessively large. However, in beveling with an emphasis placed on the amount of projection of the lens toward the front side of the rim RM, there are cases where when an attempt is made to fit the lens, for which beveling has been completed, to the rim RM, the edge on the rear surface side of the lens and a portion of the nose pad arm KA unfavorably interfere with each other, making it difficult to fit the lens to the rim RM if the edge of the lens is thick. If an attempt is made to forcedly fit the lens to the rim RM, there occur such problems as the breakage of the lens, damaging a coating on the nose pad arm KA, and making it difficult to adjust the position of the nose pad NP. Although the interference with the lens can be avoided to some extent by the deformation of the nose pad arm KA, a forced deformation can possibly result in the breakage of the attachment of the nose pad arm KA. If a bevel is processed by being offset toward the rear surface side of the lens in order to avoid the interference with the nose pad arm KA, the amount of projection of the lens toward the front side becomes large, rendering the appearance poor.
Additionally, it is difficult for general operators to predict whether or not the interference with the nose pad arm KA will occur before lens processing, and they often notice the problem only after the lens has been fitted to the rim. In the case where an interference between the nose pad arm KA and the lens has occurred, by using a manual device having a conical grindstone, a skilled operator would be able to grind off an interfering portion by applying a corner of the lens edge against the grindstone, but it is difficult for a general operator to grind the lens with good appearance.